The present invention relates to a method for preventing anhydrous potassium fluoride from solidification.
Hitherto, anhydrous potassium fluoride has been widely used as a flux in silver soldering, a reagent in introducing fluorine into organic compound, a catalyst in Michael reaction, etc.
The anhydrous potassium fluoride is essentially easy to solidify, and sometimes grows up to a large mass during the period of preservation in a packing bag making it difficulty to take it out when using, thereby requiring troublesome work of crushing the mass. Thus, there is a difficult not a little in handling anhydrous potassium fluoride in general. The anhydrous potassium fluoride is composed of a crystal structure of high hygroscopic property, and absorbs moisture to form KF.2H.sub.2 O or KF.4H.sub.2 O when the temperature is below 40.degree. C. Accordingly, it is necessary to pay attention so as to prevent the anhydrous potassium fluoride from absorbing moisture even at the time of crushing the mass thereof. It is generally said that such solidification is caused by existence of moisture, but the true cause has not been theoretically made clear yet.
Several methods have been proposed in order to prevent the solidification. As one of such methods, it is known that the anhydrous potassium fluoride is additively coated with several weight % of inorganic insoluble fine powder such as diatomite, talc, etc. to prevent fine particles of the anhydrous potassium fluoride from being in contact with one another. It is also known as another method to adhere a surfactant. In these methods, however, there is a difficulty of how to perfectly adhere additive fine particles to the anhydrous potassium fluoride, and, moreover, even if the solidification is effectively prevented thereby, there remains another problem of contamination of impurities. Thus, the foregoing known methods cannot be adopted in practical use.
Under such circumstances, more attention has been actually paid to the manner of packing up to today in order to prevent moisture absorption as much as possible thereby preventing occurrence of solidification. In this sense, it has been usually adopted that, while outer packing is prepared of a paper bag, inner polyethylene packing is formed into a double structure, or that a cap of a metallic can be soldered after inserting a content (anhydrous potassium fluoride) therein.
In any of these methods, however, solidification takes place after preservation for a week or so making it difficult to take the content out.